"Turkey, a NATO ally since 1952, significantly affects a number of key U.S. national security issues in the Middle East and Europe. U.S.-Turkey relations have worsened throughout this decade over several matters, including Syria's civil war, Turkey-Israel tensions, Turkey-Russia cooperation, and various Turkish domestic developments. The United States and NATO have military personnel and key equipment deployed to various sites in Turkey, including at Incirlik air base in the southern part of the country. Bilateral ties have reached historic lows in the summer of 2018. The major flashpoint has been a Turkish criminal case against American pastor Andrew Brunson. U.S. sanctions on Turkey related to the Brunson case and responses by Turkey and international markets appear to have seriously aggravated an already precipitous drop in the value of Turkey's currency."
CRS Report for Congress, R41368